Field of the Invention
The invention relates to a flame sensor apparatus, and specifically relates to an insulated cable for a flame sensor apparatus that senses characteristics of a flame in a combustion chamber.
Discussion of Prior Art
Within an oil or gas fueled turbine, fuel is fed into a combustion chamber within which an ignition flame is present. If the flame becomes extinguished, commonly referred to as a flame-out condition, it is undesirable for fuel to continue to be fed into the hot combustion chamber without appropriate ignition. Consequently, if the ignition flame is extinguished within the combustion chamber, the fuel feed into the combustion chamber should be quickly terminated and thus limit un-combusted fuel build up.
A flame sensor is generally used for detecting the presence or absence of an ignition flame, as well as the flame's relative intensity, within a combustion chamber of a gas turbine. Also, flame sensing electronics are commonly associated with the flame sensor within the turbine arrangement. The flame sensing electronics may be temperature sensitive and can be located a distance from the relatively hot temperature(s) in and near the combustion chamber. A low magnitude current signal from a sensor assembly near the combustion chamber can be transferred to the flame sensing electronics. The signal can be transferred via a cable assembly that is part of a sealed environment that helps preserve the low magnitude current signal. It would be useful to provide an insulated cable assembly that is capable of withstanding relatively high temperatures near the combustion chamber without losing insulation resistance.